Riyad as-Salihin, Book 9, Hadith 1124 (In-Book) ⓘ

Anas (May Allah be pleased with him) reported: In the lifetime of the Messenger of Allah, we used to perform two Rak'ah (optional prayer) after sunset before the Maghrib prayer. It was asked: "Did Messenger of Allah perform them?" He replied: "He saw us performing it, but he neither ordered us to perform them nor did he forbid us from doing so."[Muslim].

وعنه قال‏:‏ كنا نصلي على عهد رسول الله صلى الله عليه وسلم ركعتين بعد غروب الشمس قبل المغرب، فقيل‏:‏ أكان رسول الله صلى الله عليه وسلم صلاها‏؟‏ قال‏:‏ كان يرانا نصليهما فلم يأمرنا ولم ينهنا‏"‏‏.‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏